This invention relates generally to injection molding and more particularly to an elongated heated probe having a longitudinal thermocouple bore and an off center integral electrical heating element.
Heated probes which are mounted to extend into an injection molding melt passage to heat the melt flowing around it are well known in the art. As seen in the applicant's Canadian patent application Serial Number 2,032,728 filed Dec. 19, 1990 entitled "Injection Molding Probe with Varying Heat Profile" it is known to provide the electrical heating element of such a probe with different numbers of multiple runs to have a varying heat profile along its length to compensate for different amounts of heat loss. The applicant's U.S. Pat. No. 4,611,394 shows an earlier type of heated probe with a thermocouple bore running down one side.
Heated nozzles in which the melt passage extends through the nozzle are also well known in the art. The distinction between a nozzle and a probe is that the melt passage extends through a nozzle, whereas it flows around a probe. A nozzle for valve gating is shown in U.S. Pat. No. 4,712,995 to Basnett which issued Dec. 15, 1987. In this case, the heating element and melt passage are off center to provide for the center gating valve pin.
Recent increasing demand for multi-cavity injection molding systems having greater numbers of cavities has made smaller component size of even more critical importance. At the same time, the increasing use of temperature critical materials has also made accurate temperature monitoring very critical. Therefore, it is very advantageous to position a thermocouple in a forward portion of the body of the probe itself without unnecessarily increasing the outer diameter of the body of the probe. Accurate location of the probe in the well and reliable retention of the thermocouple wire in the thermocouple bore have also been problems. Efficiently providing additional heat to the area of an off center gate is also very desirable in some instances.